1 RT 255 C Cross Sectional Anatomy Week 1 FINAL

2 Name the Sectional Planes A B C D

3 Oblique and Transverse Used for imaging of heart. Commonly used in MR and sonography

4 Axial (Transverse) Planes –1–1 –2–2 –3–3 –4–4 –5–5 –6–6

5 Axial Scout

6

7 Axial (cross sectional)

8 Sagittal Plane 1 2 3

9 Sagittal Scout

10 Sagittal

11 Coronal Plane

12 Coronal

13

14 Coronal

15 Name the Imaging Plane

16

17

18

19

20

21

22

23

24

25

26 Both Radiation: Why CT vs. Radiography Superimposition Contrast Resolution –Less scatter One exposure

27 Similar to Radiography Radiopaque are white –Bone –Prosthesis Lower density images are gray –Fat –Muscles –Organs Very low density are black –Air

28 Hounsfield Units

29 Fundamentals of CT Cross sectional Tube rotates around patient Detectors measures primary data Primary data sent to computer Calculated according to algorithm Data assembled into a matrix Each sectional slice is displaced on cathode ray tube

30 Generations of Scanners First generation –1–1 –2–2 –3–3 –4–4 Second generation –1–1 –2–2 –3–3 –4–4

31 Third Generation Rotate/ rotate More than 750 detectors 1-10 seconds

32 Fourth Generation Rotate only Fixed detectors More detectors Higher dose to PT

33 Technical Aspects Remnant radiation is collected –1–1 –2–2 Electrical signal digitized –Each signal assigned a number Signals combined to form digital image –Field of View (FOV) determines amount of data to be displayed on monitor

34 Breakdown of the Digital Image Array of numbers –1–1 Pixel –1–1 –2–2 Voxel –1–1 –2–2 –3–3

35 System Components Computer –Operators console Gantry Table

36 Computer Four basic functions –1. –2–2 –3–3 –4–4

37 Data Acquisition Tech chooses various parameters –1 –2 –3 –4

38 Image Reconstruction Digitizes raw data Computer performs mathematical computations on a temporary storage system –Host computer has limited storage capacity Reconstruction takes a few seconds

39 Long term Storage After reconstruction it is transferred to another storage medium Those temporary images on the host computer are archived separately as an independent study that can be retrieved later

40 Image display Can be viewed on a video monitor Tech and doctor can communicate with host computer to view images Can manipulate images –1–1 –2–2 –Image resolution lost with reconstruction in other planes

41 Gantry Circular Aperture is the hole PT goes in Houses –Detector, slip ring, generator and x-ray tube Tube similar to x-ray tube –Must withstand higher amounts of heat Can be tilted 30 degrees forward and back

42 Table Automated device linked to gantry & computer Moves in increments –According to protocol Made of wood or low density carbon composite Has a weight limit

43 Control Console Where the tech controls the scanner Has a keyboard, display monitor & mouse Allows tech to control –1. –2 –3 –4

44 Image Manipulation Windowing –1. Window width –1–1 –2–2 –3–3 Window level –1–1 –2–2

45 Windowing Window width 400 Window level 35 Window width 2200 Window level 400

46 Factors Affecting Image Quality Spatial resolution Contrast resolution Noise Artifacts Patient factors Scan times Scan diameter

47 Spatial Resolution What happens to resolution with smaller phosphor crystals in standard film screen systems? Is a function of pixel size –Smaller: better detail Thinner slices: increased detail

48 Contrast Resolution and Noise Ability to distinguish adjacent tissue In CT it is better than in conventional x-ray –Less scatter Appears as graininess Low noise is smooth to the eye High noise is blotchy and spotty As noise increases contrast resolution decreases

49 Artifacts Streak artifacts –Metallic objects, pacemakers, and prosthesis High concentration barium

50 Patient Factors Motion Size of patient

51 Image Quality under Tech Control Slice thickness Scan time Scan diameters

52 Diagnostic Applications Most common anatomy examined is –Head, chest and abdomen Exam of choice for: –Head trauma –CVA Also useful for: –Infarctions –Hemorrhage –Disk herniations –Craniofacial fractures and tumors –Cancers –Hydrocephalus –Degenerative diseases –Inflammatory infections –Congenital disorders

53 Use of Contrast Media Can be administered orally, rectally and intravenously IV usually non-ionic contrast BA and Hypaque used for abdomen and GI studies. –2% concentration BA –Low concentration (hypaque)

54 Special Features Dynamic scanning CT angiography (CTA) Spiral/helical CT Multi-slice Spiral/helical CT 3 D imaging Radiation therapy treatment

55 Dynamic Scanning and CTA After contrast administration Sequential scanning times as different structures enhance CTA: –1–1 –2–2 –3–3

56 CTA

57 CTA

58 Spiral / Helical CT and Multi-slice Spiral/ Helical CT Single row of detectors Gantry rotates around PT as table moves Scans a volume instead of slices Better detail Fast scan times –For peds and combative patients Multiple rows of detector arrays A four row scanner would scan 4 times faster Improced spatial resolution LG areas of body can be done with one breath hold

59 Spiral and Multi-slice Spiral

60 3D Imaging Postprocessing technique Takes 2D raw data and constructs a 3D image

61 3D imaging

62 3D Imaging

63 Radiation Therapy Planning Gives volumetric and depth calculation ability Allows for one CT instead of the 3 they used to do Flat board used instead of curved couch Dose to normal tissue is minimized

64 RAD Therapy and CT

65 RAD Therapy and CT

66 CT and Radiation Dose CT doses are higher than conventional radiography A lower pitch results in a higher dose –More overlap Thinner slices also result in a higher dose

67 CT vs. MRI MRI exhibits better low contrast than CT Higher cost and takes longer Cannot do with metal CT demonstrates bone better than MRI Faster, so preferred for some PT’s –Small gantry –Wide aperture Less costly

68 The Future of CT Has significantly increased in the past 5 years Higher quality images increase accuracy of diagnosis and treatment Cost effective Will continue to be a diagnostic tool